You Are What you Eat - A Nutrition Primer

author : TriDoc5280
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This article will cover the basics on the nutritional needs of athletes and will include some standard recommendations from neutral bodies.

You are what you eat. As an aphorism, these words are very appropriate to those who live an active lifestyle including triathletes. For this reason, knowing what it is that you eat, and knowing what it is that you should eat are important elements for a successful training regimen. There are many sources for nutritional information out there and as always it is best to maintain a healthy level of skepticism depending on what the source is. Manufacturers of supplements or sport drinks may have their bottom line as a higher priority than your actual nutritional needs. Hence it is always best to find an unbiased neutral source.

Rather than try to provide an extensive dissertation on the nutritional needs of athletes, this article will cover the basics and include some standard recommendations from neutral bodies.

Why we need to eat
Eating is one of the more pleasurable things that we do on a daily basis. But in addition to providing important emotional and social benefits, eating also provides our bodies with two important things; fuel for cellular processes and the building blocks for new tissue growth and the repair of older tissues.

Every cell in the body has ongoing biochemical processes that relate to their primary function. These processes require energy that is obtained from the food that we eat. Furthermore, basic cellular functions produce many waste products some of which are injurious. As cellular structures become damaged their repair is made possible by the provision of energy and building materials derived from the food we eat.

Finally, in order to grow, cells must divide innumerably. Each new cell is made up of the molecules and complex structures formed from the chemical elements in the foods that we eat.

Why we need to eat right
Everything that passes our lips enters our body and is subject to one of two possible fates: 1) It is absorbed or 2) It passes through the colon unaltered and is excreted as fecal material.

All matter that is absorbed passes through the liver for detoxification. This organ functions essentially as a huge toxin sponge and is critical to our survival. Unfortunately, because it concentrates all the toxins that we eat, the liver is also extremely susceptible to injury if we ingest too much of anything that is harmful to this organ.

Beyond the liver, it is vital that our tissues receive everything that they need in order to function properly. Too much of anything is almost as bad as too little. Moderation is key. Improper eating habits, eating too much of any one type of nutrient or toxin or too little of certain vital nutrients, cause many different disease states. Depending on the nutrient involved the effects may be life threatening. Obesity results from a diet too high in fat and is associated with diabetes, heart disease and certain types of cancers. Too much protein may precipitate kidney problems, too little vitamin D causes rickets while an absence of vitamin C causes connective tissue disease known as scurvy.

With the abundance of food available to those in western societies, diseases caused by undernourishment are all but unheard of while those of over-nourishment have become far too common.

What do we eat
Everything that we eat is composed of essentially the same types of molecules. How much of each type of molecule determines taste, texture and nutritional value. All foods are made up of:

  • Fats

  • Carbohydrates (sugars)

  • Protein

  • Fiber

  • Vitamins

  • Water

  • Electrolytes

  • Chemical additives principally in the forms of flavors, coloring and preservatives

Our bodies require all of these save the last in varying quantities. I will deal with each in turn.

Fats consist of many types of complex molecules principally made of carbon and hydrogen. Fats are an essential part of a human diet as they provide a high-energy content. However, since it is difficult to metabolize fat, the body usually stores it for times when other, more desirable sources are scarce.

Fats can be grouped according to their type:

  • Unsaturated fats

  • Saturated fats

  • Essential fats

  • Cholesterols

Saturated fats are the least useful of the group and most likely to contribute to disease if ingested in large quantities. Essential fats are molecules that are required by cells for structural integrity but are not manufactured in the body. They must be found in the diet for good health. Cholesterol is a vital component of cell walls and is a required element of a healthy diet. Too much cholesterol leads to disease though and so as noted earlier, moderation is the key.

National guidelines for fat intake suggest that the maximum should be less than 30% of total calories with saturated fats constituting less than 10%. In a typical western diet, fats have come to comprise almost 40% of the daily caloric intake. This represents eating a stick of butter each and every day. In order to achieve the recommended levels, it is helpful to know where our fat intake comes from.

Animal products provide the most abundant source of fats in the diet. Meat, dairy products and oils all are high in fat and are particularly high in saturated fats. Poultry, fish, fruits and vegetables are low in fat and provide predominantly unsaturated fats.

Athletes generally avoid foods with high fat contents but they should not eliminate fat completely. As noted earlier, some fats are essential for survival and these must be included in every athlete’s diet. Furthermore, for triathletes in particular, fats provide an important source of energy in longer distance events. Finally, fats are also required to dissolve certain vitamins, specifically, A, D, E & K. Without fat in our diet we would not get these vitamins.

Sugars are the primary fuel used by all cells in the body for energy. Over billions of years our cells have become supremely adapted to extract every last bit of energy contained within the many bonds of these complex molecules. Although sugars exist in many forms, once ingested they are all converted to glucose prior to being used as cellular fuel. Although carbohydrates contain less energy per gram than do fats, that energy is much more easily extracted and readily converted to cellular needs and so carbohydrates remain a very important component of diet and should represent anywhere from 46-65% of daily caloric intake. Low carb diet fads are NOT for athletes, as this serves only to rob the body of the energy it needs to maintain high levels of activity.

Unfortunately, carbohydrates are difficult to store so when conditions of decreased intake occur, what little stores are available are rapidly depleted. This has an important impact on distance athletes who need to take in high levels of carbohydrates beginning one to two hours into an event as this is when stores begin to run low.

Carbohydrates exist in two forms in our diet; simple and complex. Simple carbohydrates are found in fruits and vegetables and grains and in refined form in everything from candy bars to cakes.

Complex carbohydrates are simply long strings of simple carbohydrates. Because these take longer to process in our bodies, they provide a less readily available but more sustained form of energy. Examples include starchy foods such as potatoes and pasta as well as many of the commercially available sports gels and drinks.

10-35% of daily calories should be in the form of protein. Protein is the building block for muscles and while simply eating large amounts of protein will not result in muscle formation, exercising without adequate intake of protein will not be fruitful as muscle wasting will occur.

Protein is most commonly ingested in the forms of meat, poultry or fish. Vegetarians obtain their protein from tofu and other soy products. Commercially available protein formulations are principally composed of whey, a milk derived protein. Whey is also found in many protein meal supplement bars.

Too much protein, in excess of 2g/kg/day, may result in a build up of nitrogen compounds that can overload and injure the kidneys. Thus, this should be avoided.

Found in all fruits and vegetables in varying quantities, fiber is the major unabsorbed component of our diet and contributes the majority of the formed substance in fecal matter. Too little fiber in the diet can result in constipation while too much may precipitate diarrhea. There has been no definitively proven link between high dietary fiber and lower rates of colon cancer.

Vitamins are chemical compounds that serve as important co-enzymes in many chemical processes in the body. All are needed in small quantities on a daily basis.

Here is a partial list of commonly discussed vitamins along with their principal functions and where they may be found:

A: Necessary for color and night vision. Found in orange and yellow vegetables.
B complex: A series of vitamins the most important of which are B1, B6 and B12. B1 & B6 are required for neurological function while B12 has an important role in blood cell formation. B vitamins are found in grains and meats. Most breads and cereals are fortified with B1 and B6. B12 is obtained principally from meats.
C: A free radical scavenger, vitamin C has important functions for connective tissue disease maturation and has a role in immune function. It is found principally in citrus fruits.
D: Required for proper bone development. Synthesized in the body when the skin is exposed to sunlight it is also found in milk.
E: Another free radical scavenger, this vitamin has an important role in protecting against the formation of mutated DNA. Vitamin E is found in nuts, vegetables, fish and other meats.
K: Vitamin K is important for the formation of important proteins that control bleeding. It too is found principally in nuts and vegetables.

As always, too much or too little quantities of ingested vitamins can lead to disease. With a normal western diet, the addition of vitamin supplements is completely unnecessary (and potentially injurious) in order to obtain the recommended daily levels. Some science has suggested that higher levels of vitamin C may be beneficial in staving off viral illnesses but this has never been proven conclusively.

Water & electrolytes
Fully two thirds of our bodies are made up of water. Although most people think of only the blood comprising mostly of water, this is in actuality only a small fraction of the total. The vast majority of water is found within and between our cells. In fact, human physiology has evolved over millions of years to finely maintain a near constant amount of water in our bodies at all times. To do this, water losses that are constantly ongoing must be offset by water intake.

Water is lost as sweat, urine, feces and as vapor in our breath. Water intake is through drinking and eating as foods also contain fairly high water content. Although the actual amounts lost will vary depending on many environmental factors, the average daily water loss for a healthy adult is 2.5 liters. About 20% of this is replaced in the form of food and the rest through consuming beverages. For athletes, the amount of water lost is substantially higher given the increased losses through sweat and breathing. Thus most athletes need to drink at least two liters of water every day.

Electrolytes are the elements dissolved in water that are required in our cells for all manner of processes. Sodium and potassium are the two most abundant electrolytes in all cellular material so the consumption of fruits, vegetables and meats will easily allow anyone to replace ongoing losses.

Calcium is another important electrolyte and is also required in fairly large amounts. Increased intake of calcium is primarily important in women, especially those with a family history of osteoporosis.

Iron is an integral component of our blood cells and must be obtained every day either through the consumption of meat or other iron rich foods. Vegetarian men need not worry about iron deficiency though women vegetarians should discuss the need for supplementation with their doctors.

Chemical additives
Flavor, color and smell enhancement along with freshness maintenance and texture modification are the main reasons that manufacturers add chemicals to our food. Most of the time, these chemicals are added in very small quantities and either pass through our bodies without causing any effects or are absorbed in such small amounts that their presence is insignificant.

Although there has never been any scientific evidence that these chemical additives cause any harm, many people remain wary of putting anything in their bodies that didn’t arise naturally in the ingredients. It is true that chemical additives are for the most part unnecessary for our diets, the exception being those preservatives that prevent spoilage and resultant illness, so the choice to eat them is individual and there is no right or wrong.

In summary, making the right choices about what to eat are as important as they are complicated. Although fad diets and ‘athlete diets’ come and go, the best way to maintain good health is to be smart about what you eat. Doing this means having a better understanding of the what and the why of our food but also in taking the time to read the labels on everything you buy in order to ensure that the foods you eat are what you want them to be.

The single best rule to live by with respect to diet is that moderation is key. Too much or too little of anything is always a bad thing.

Train hard, train healthy.

Next month: Training and illness. Separating fact from fiction.


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date: April 2, 2006


Long time triathlete with multiple IM finishes and over 30 HIM since 2001. 70.3 WC x4, Kona x 1.

Previous medical contributor to Triathlete Magazine and Inside Triathlon now the author and producer of the TriDoc podcast on iTunes, Google Play and Stitcher


Long time triathlete with multiple IM finishes and over 30 HIM since 2001. 70.3 WC x4, Kona x 1.

Previous medical contributor to Triathlete Magazine and Inside Triathlon now the author and producer of the TriDoc podcast on iTunes, Google Play and Stitcher

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